1. Technical Field
This disclosure relates to a rechargeable lithium.
2. Description of the Related Art
Recently, portable electronic devices (such as cell phones, laptop computers, tablet PCs, and the like) are becoming smaller and lighter, increasing the demand for batteries with high-capacity as power sources. In response to this demand, non-aqueous electrolyte rechargeable lithium batteries using non-aqueous electrolytes and transporting lithium ions between positive and negative electrodes have been widely used as rechargeable batteries having high power and high energy density. As the positive active material, the non-aqueous electrolyte rechargeable lithium battery uses an oxide capable of intercalating lithium ions, such as those made from lithium and transition elements, for example, LiCoO2, LiMn2O4, LiNi1−xCoxO2 (0<x<1), and the like. As the negative active material, the non-aqueous electrolyte rechargeable lithium battery may include artificial or natural graphite for intercalating/deintercalating lithium, a carbon-based material such as hard carbon, or a material capable of alloying with lithium (such as Si, Sn, or the like), and the like. However, the use of portable electronic devices for playing motion pictures, games, and the like is increasing, and the devices tend to consume more electricity when used for these tasks. Thus, portable electronic devices require batteries with high-capacity as power sources. The non-aqueous electrolyte rechargeable lithium battery may achieve high-capacity by 1) increasing the capacity of an active material, 2) increasing the charge voltage, 3) increasing the charge amount of the active material and thus, the charge density, and the like. However, these methods have certain challenges, for example, the method of increasing the charge voltage of an active material decomposes the electrolyte. In particular, when the active material is stored at high temperatures, or is continually charged, the electrolyte may be decomposed and generate gas, thus expanding the battery or increasing internal pressure of the battery. Accordingly, attempts to ensure the safety of the battery have continually been made by using an additive to increase the flash point and delay firing, and to decrease thickness changes, thus improving thermal impact durability.